During the past decade, ashless sludge dispersants have become increasingly important, primarily in improving the performance of lubricants and gasoline in keeping the engine clean of deposits, and permitting extended crankcase oil drain periods. Most commercial ashless dispersants fall into several general categories. In one category, an amine or polyamine is attached to a long chain hydrocarbon polymer, usually polyisobutylene, obtained by the reaction of halogenated olefin polymer with polyamine as in U.S. Pat. Nos. 3,275,554; 3,565,592; 3,565,804. In another category, a polyamine is linked to the polyisobutylene through an acid group, such as long chain monocarboxylic acid, e.g., see U.S. Pat. No. 3,444,170 or long chain dicarboxylic acid such as polyisobutenylsuccinic anhydride, by forming amide or imide linkages, such as described in U.S. Pat. Nos. 3,172,892; 3,219,666; etc. More recently, non-nitrogen ashless dispersants have been formed by esterifying long chain dicarboxylic acids; such as the polyisobutenylsuccinic anhydride, with polyols, such as pentaerythritol, as in U.S. Pat. No. 3,381,022.
Reaction products of hydrocarbon substituted succinic anhydride, e.g., the aforesaid polyisobutenylsuccinic anhydride, with compounds containing both an amine group and a hydroxy group have been suggested or investigated in the prior art. For example, U.S. Pat. No. 3,272,746 teaches the reaction of ethanolamine and diethanolamine, as well as various hydroxyalkyl substituted alkylene amines, such as N-(2-hydroxyethyl) ethylene diamine, N,N'-bis(2-hydroxyethyl) ethylene diamine, with alkenyl succinic anhydride to obtain ashless dispersants for lube oil. A hydroxy amine, such as diethanolamine, is reacted with a long chain alkenylsuccinic anhydride in U.S. Pat. No. 3,324,033 to form a mixture of esters and amides, wherein some of the diethanolamine reacts through a hydroxy group to given an ester linkage, which another portion of the diethanolamine forms an amide linkage. U.S. Pat. No. 3,364,001 teaches a tertiary alkanolamine reacted with an alkenyl succinic anhydride to form an ester useful as a gasoline additive. U.S. Pat. No. 3,448,049 teaches dispersants, corrosion inhibitors and antiwear agents in lubricants and fuels by esterifying alkenyl succinic anhydride with a hydroxy compound made by reacting an alkanolamine with an unsaturated ester, amide or nitrile. U.S. Pat. No. 3,630,904 teaches reacting a hydroxy amine, with both short and long chain dicarboxylic acid. U.S. Pat. No. 3,484,374 teaches the polymeric condensation products of polycarboxylic acid or anhydride with various alkanolamines such as aminoethylethanolamine. N-methyldiethanolamine, etc. United Kingdom Specification No. 809,001 teaches corrosion inhibitors comprising a multiple salt complex derived from the reaction product of hydrocarbyl substituted dicarboxylic acids and hydroxy amines (including 2-amino-2-methyl-1,3-propanediol [AMP] and tris hydroxymethylaminomethane [THAM]) further complexed with mono- and polycarboxylic acids (see Examples 17-19).
U.S. Pat. No. 3,576,743 teaches reacting polyisobutenylsuccinic anhydride with a polyol, such as pentaerythritol, followed by reaction with THAM, (see Example 1). U.S. Pat. No. 3,632,511 teaches reacting polyisobutenylsuccinic anhydride with both a polyamine and a polyhydric alcohol including THAM. U.S. Pat. No. 3,697,428 (Example 11) teaches reacting polyisobutenylsuccinic anhydride with a mixture of pentaerythritol and THAM. United Kingdom Specification No. 948,409 teaches ashless, amide/imide/ester type lubricant additives prepared by reacting an alkenyl succinic anhydride, said alkenyl group having 30 to 700 carbon atoms, with a hydroxy amine including THAM.